Context: Epidemiological data suggest a genetic susceptibility to thyroid antibody (TAb) production.

Objective: The objective of the study was to identify genetic loci that are linked with TAb production.

Design: The design of the study was a whole genome linkage study in families with clustering of thyroid autoimmunity.

Settings: The study took place at an academic medical center.

Participants: Participants included 102 multigenerational families (540 individuals) multiplex for autoimmune thyroid disease (AITD) and TAb production.

Main Outcome Measures: We computed two-point logarithm of odds (LOD) scores and multipoint heterogeneity LOD scores for 400 microsatellite markers spanning the entire human genome at an average distance of 10 cm (∼10 Mb).

Results: Three loci showed evidence for linkage with TAb production: 1) 2q locus, which gave a maximum multipoint heterogeneity LOD score (HLOD) of 2.8 and contained the CTLA-4 gene, previously reported to be linked and associated with clinical AITD; (2) 6p locus (HLOD 2.5), which was the same AITD-1 locus found to be linked with clinical AITD; and (3) 8q locus (HLOD 2.2), which contained the thyroglobulin gene, also previously reported to be linked and associated with AITD. All loci that were linked to TAb were also linked to AITD, suggesting that TAb and AITD share the same genetic predisposition.

Conclusions: We conclude that: 1) some of the genes/loci predisposing to TAb and AITD are shared, whereas distinct genes/loci also exist; (2) the presence of TAb in relatives of AITD patients may be associated with increased risk for the development of clinical AITD; and (3) further studies are needed to determine the predictive value of TAb levels for the development of clinical AITD in relatives of patients with familial AITD.